Investigation of the role of southwestern Asia dust events on urban air pollution: a case study of Ahvaz, a highly polluted city.

Investigating aerosol composition and particle dynamics in densely populated and polluted urban centers is crucial for understanding and managing urban air quality. Ahvaz, in southwestern Iran, consistently ranks among the most polluted cities globally, primarily due to high PM concentrations. This study analyzes trends in suspended particle concentrations in Ahvaz over a 12-year period (2008-2019) to identify the contributions of natural and anthropogenic sources to air pollution. Diurnal, monthly, and annual variations in PM and PM levels were examined, revealing key insights into the city's pollution dynamics. Diurnal PM peaks around noon (232 µg/m), mainly driven by natural dust sources, with minimal anthropogenic impact indicated by similar weekend and weekday concentrations (only 1.5% difference). Monthly analysis reveals significant dust activity in June and July (maximum PM concentration of 388.18 µg/m), while higher PM levels in winter (average 54.8 µg/m) are attributed to fossil fuel combustion. The PM/PM ratio (mean = 0.24) highlights the dominance of coarse particles from dust events, especially in summer. The Hoffmann classification identifies 3425 dusty days in the study period, with PM levels notably higher due to dust sources in southern Iraq and southwestern Iran. Seasonal wind patterns, particularly Shamal winds, facilitate dust transport, corroborated by Windrose and PM rose data. The study underscores the need for regional dust suppression strategies in southern Iraq and southwestern Iran to mitigate air pollution in Ahvaz, highlighting the importance of regional cooperation.